Such axial flow fans are generally provided with a plurality of blades, each of which is secured at its root to a hub that is driven by a rotating shaft and from which the blade extends radially outwardly. The blades can be spaced around the hub in a symmetrical or non-symmetrical fashion. Axial flow fans are known having blades of various designs. Thus, the blades can be provided with a tangential sweep either in the forward or rearward direction, with variations in pitch angle to suit particular applications. Furthermore, it is known to secure the blade tips to an outer circular band which encloses the blades and is generally centered on the axis of rotation of the fan.
When used in a vehicular application, the fan can be arranged either to blow air through a heat exchange system if the heat exchange system is on the high-pressure (downstream) side of the fan or draw air through the heat exchange system if the heat exchange system is on the low-pressure (upstream) side of the fan. Such fans can be made from moulded plastics or from sheet metal or a combination of the two.
Reference is made to the following documents which describe fans designed particularly for vehicular cooling applications. U.S. Pat. No. 4,358,245, U.S. Pat. No. 4,569,631 and U.S. Pat. No. 4,569,632 disclose a fan of the general type with which the present invention is concerned. In each case, the fan hub comprises a cylindrical hub section providing an aperture centrally of the hub section for receiving a motor shaft by means of which the hub can be rotated. In U.S. Pat. No. 4,548,548, a motor is mounted to a separate housing which is then located within the hub section. GB-A-2178798 also describes a hub having a conventional cylindrical section with an aperture for receiving a shaft.
A first object of the present invention is to provide a fan hub capable of securely locating a shaft to reduce the play between the shaft and the hub and thus to resist relative rotation between the shaft and the hub.
A second object of the present invention is to provide a fan hub which can be manufactured simply.
A third object of the present invention (at least in the preferred embodiment) is to provide a hub in which a motor front plate is protected from dust and moisture.
A fourth object of the present invention (at least in the preferred embodiment) is to reduce the vortex along the surface of the hub and to create less turbulence within the body of the fan.